Titanium tetrahalide compounds have long been used for olefin polymerization and have found particular utility in the polymerization of propylene although they have also found utility in the polymerization of ethylene. Generally, such catalyst systems exhibit sensitivity to hydrogen and other materials which have been found to act as molecular weight control agents whereby on incorporation of a small amount of such agents, higher melt flow polymers are obtained. In general, this is desirable although there are instances where it would be desirable to have a catalyst which is not sensitive to molecular weight control agents. Such a catalyst would be of value as one component of a mixed catalyst system for obtaining a polymer with broad molecular weight distribution.